This invention pertains to air bearing devices for handling large objects and more particularly to large objects mounted on wheels.
Historically, the installation of an engine in a jet aircraft involved a process that required considerable time-consuming maneuvering. Typically a jet engine is shipped in a cylindrical container which contains the engine and its own support dolly. At the point of destination, the engine and dolly, in combination, are removed from the shipping container and placed on a four-wheel transport device for further movement, either to storage or the assembly line. Typical of these transport devices is the Air Log Model 4000 engine dolly, or equivalent, which is widely used by aircraft manufacturers, airlines, and the military for transporting and installing engines. While many of these wheeled engine transporters are provided with devices for three axes of movement of the engine, engine installation requires precise alignment of the engine to the aircraft support structure. The weight and cumbersomeness of the transport dolly, the engine dolly, and the engine makes maneuvering difficult. Precise alignment of the engine to the engine mounting structure is necessary to avoid overstressing the engine support structure. This issue was highlighted by the tragic aircraft accident in Chicago in June, 1979, which was alleged to be caused by overstressing the engine pylon support structure during engine replacement.
Perhaps the closest prior art in function is the apparatus described in Aviation Week and Space Technology, Dec. 21, 1981. While this apparatus differs substantially in approach and structure to the instant invention, it exemplifies the problem.
The closest known prior art in teaching is U.S. Pat. No. 4,240,773, issued to Terry, co-inventor of the instant invention. That apparatus is directed to handling large rolls of paper and requires a great deal of space on either side of the roll to be lifted. The reference teaches two arms which slideably mount on a cross member and are driven by two pneumatic cylinders to grasp the paper roll as opposed to a pair of chocks in the instant invention, one of which is pneumatically actuated by a bladder to engage the wheel. Of much greater importance, the reference uses four air bearing pads, two on each side of the torus. Since, three points establish a plane, this apparatus is stable but requires considerably more space around the wheel to be lifted. In the subject invention, two air bearings are used, one on each side of the wheel and requires a third point for support to react the overturning moment. The third point is provided by either an arm attached to the base which terminates in a hook engaging the perimeter of the wheel, generally opposite the chocks, or in the alternate embodiment, a reaction point is provided against the structure of the vehicle to be lifted. The net result is that the apparatus of this device is smaller requiring less clearance, easier to handle, and cheaper, as it eliminates one of the air bearings.
Of course, the application of this wheel lift is not limited to engine installation and removal. It applies equally well to dollies or wheeled fixtures which support large heavy major aircraft assemblies which need to be joined together and require matching interfacing parts.
It is an important object of the present invention to provide an air bearing wheel lift device which is applied at each wheel of a multiple wheeled transporter so as to permit translation of the transporter in any direction parallel to the supporting floor when the air bearing are energized.
It is another object of this invention to provide a wheel lift which is light enough in weight for one man to handle, and small enough to clear the attaching structure of most vehicles.
Another object of this invention is to provide a wheel lift adaptable to essentially any size wheel or vehicle.